The relationship that exists between circulating and oviduct tissue levels of estrone, estradiol-17 Beta, and progesterone during the ovum transport period will be determined by radioimmunoassay. Antibodies to estradiol-17 Beta, estrone, and progesterone will be used to study the hormonal requirements for normal ovum transport through the rabbit oviduct. Antisera against three hormones will be produced in ovariectomized sheep, characterized as to specificity and titre, and injected into rabbits singly or in combination to cause a passive immunity. The result of passive immunity on ovum transport and ova plasma and oviduct tissue levels of the three steroids will be determined.